Comments on: Increasing our Solar Thermal System vs. Gas Boiler Backup

By: Your Questions About New Modern House Plans | Home Design News

Your Questions About New Modern House Plans | Home Design News — Sat, 24 Sep 2011 01:02:16 +0000

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By: Kris

Kris — Sat, 04 Dec 2010 23:26:06 +0000

Since we had to excavate 4 feet down for footings, we just had them scoop out the center. We then insulated the bottom and sides (4″ foam), filled it with sand and 2 layers of Pex and then capped it with 4″ foam (we call it our thermal vault). The slab will be poured on top. We will pump heat into it in the summer months and then pull it out at the start of winter. We have a small basement area to act as utility space and it has 2 large tanks we have repurposed (one was an old dairy tank and we were able to pick them up for cheap) and will be outfitting with copper heating coils. This will act as short term storage during the colder months when we want to take advantage of a sunny day and store away heat for the next cloudy days.

Bob Ramlow in Wisconsin has done a lot of houses using the sand bed system except his have been uninsulated on top so by September or October heat starts to just passively transfer up into tthe living space which can result in overheating (which is usually solved by opening windows or turning on AC which seems crazy to me). We want to have better control of the heat and we won’t have any AC in the house so the thermal vault concept was much more appealing.

We are just getting blog up and running (only about 3 posts) but I’ll try to post a link later. We certainly aren’t as trim a budget as you, but then again we are building what will hopefully be our final house, our dream house. We are putting lots of sweat equity into it.

By: Chad Ludeman

Chad Ludeman — Sat, 04 Dec 2010 11:20:25 +0000

Kris – What do you do with your excess solar heat during the summer months when you are getting much more heat gain than the winter?

By: Kris

Kris — Sat, 04 Dec 2010 06:35:10 +0000

Increasing the size of your solar thermal array without a significant increase in ways to store the heat for when you need it seems like a waste of money. Most people using solar thermal to supply significant space heating use water tanks that are much larger than the typical hot water heater and/or sand beds to store heat during the sunny months for use during cloudy times. I don’t know what PA is like but in MN we need to have a way to store the solar energy from July/August for use during the typically cloudy November/December. By January it is usually very sunny again. A word of caution to people planning for solar thermal systems, make sure you do your homework. There have been a lot of poorly designed systems installed in the past 30 years. I am a huge fan of solar thermal and we are going to depend on it for most of our heating but it has taken a lot of careful planning/design. I’ll be interested in continuing to read about what you ultimately decided to do and how it has worked out for you.

By: tom toolbag

tom toolbag — Tue, 06 Jan 2009 03:19:33 +0000

I stumbled across a website called Solarcrete. They have a wall system that uses rebar and foam covered in spray-on concrete. A lot of swimming pools use spray on concrete, and molded /formed foam covered with spray on concrete is used for decorative rocks in indoor fountains. At a certain thickness, it is fire rated(I think) and dye could be mixed in to act as a color base, like a primer. I don’t know how it could be inspected other than to have a building inspector on-site when it is sprayed on, maybe there is some sort of depth gauge that they tack on to show the finish depth and then you snap it off. The Solarcrete company is about 45min. from me so I would be a moron not to see their system going up and it’s finish. There is also a link to a pv company named Atlantis Energy, they have a combined heat and power system that I’ve been thinking about for 5-10 years(go figure, somebody beat me to it). It’s a pv flat roof tile over a pex tubing layout for solar thermal. I couldn’t give you any specs because I haven’t contacted them or studied their info. I did e-mail Solarcrete to see if that system could be used below-grade and they just gave me a basic formal response without any answers. I guess that I didn’t come across like a sale, just a sight-seer.

By: chad

chad — Tue, 06 Jan 2009 02:04:12 +0000

Excellent points. Tell me more about these shot-crete walls you speak of. I like the sound of it.

By: tom toolbag

tom toolbag — Tue, 06 Jan 2009 00:40:36 +0000

This type of building works well but could use some improvements. The south facing casement windows usually had heavy condensation on them in the winter. This was due to the design and lack of completeness of the design. the exterior walls were insulated but the ceiling(underside of the roof)wasn’t. It had soffitt vents and a continuous ridge vent and I think that was where the problem was. I think we should have insulated the roof, and either sheeted the underside of the trusses(we didn’t) and used a white or light color(we used dark brown) shingles so as to keep the exterior walls and air space complete and moisture free. It would be like putting a ziplock sandwich bag inside of a ziplock freezer bag, then a spacer on the outside of the freezer bag under the roofing material. The condensation would collect on the glass, but moisture had to be in the air for it to collect somewhere(the glass). No humidity, no condensation. Knowing what I know now(I was 18 then and had no knowledge or experience then) I would put the vapor barrior on the exterior side of the outside wall, create an air space under the (white)roofing, such as a fir strip, and then also on the exterior side of the interior walls and ceiling. I would use spray-in foam insulation on the exterior walls and roof, 1/4″ sheeting on the exterior of the interior walls, 1″ foam board on the interior of the interior walls with 1″-2″ of shot-crete on all the walls instead of drywall. I think drywall is too labor and manufacturing intensive now and has outlived it’s greatest benefits by far. My theory is if you can control moisture, contain heat/repel heat with the exterior wall, and hot goes to cold, the interior wall does not have to be insulated as much(less heat loss or transfer) if the temp on the other side is nearly the same. You would need a hrv to cycle in fresh air to the living area, and erv to cycle air into and remove humidity in the air space. My plan for this was to build a house like this, get it up fast using the types of technology available now, let it sit and moniter the conditions for needs throught the weather cycles. In other words, build in early spring, let it sit through the summer and winter seasons to see what was ACTUALY needed for cooling/humidity control, and how much heat is needed. The overall timespan would be 12 mos min plus build time. All hvac systems would be broken down into: cool/humidity removal, and heat humidity addition. That takes the calculations and precision out of the process. You would need systems that could be upgraded in increments to make this work. My reasoning is this: if you take a 24 hour period and chart the temps on it you want it to be as strightline as possible. There should be no peaks or valleys, like when a system turns on and off. Why have a furnace or a/c system that can change 5-10 degrees of temp real fast, when a few tiny systems could run more often to maitain a 1-2 degree range. An example is a whole house boiler system for floor radient heating. If there is a manifold and electronic controls for zoning the house(some areas on/some off) then a boiler big enough for the whole house wouldn’t be needed. I’m imaging something the size of a tabletop gas grill for different zones running sporadically. Another idea is why not have circulation pumps that can reverse the flow from the boiler instead of heating the system from one end. My idea is to use an oversized pilot light sized flame to heat the water instead of a large boiler type to get there real fast. One big problem is that there aren’t any systems like this on the market. My idea of letting a house sit for one year is the only way I know of to properly size hvac systems and still (hopefully) satisfy building inspectors/departments. A conventionally built home might take 3-6 mos to build, so in my situation losing 6 mos is worth it, because time is cheaper than expensive systems, especially if they aren’t needed. It’s the right tool for the right job mentality.

Here’s some other points to ponder:

why put a concrete floor in the basement? With a crawlspace, concrete isn’t needed. It’s a lot of overkill to use just as a floor unless you need it for massive weight such as a hot-tub.

why design a roof to carry a certain load instead of designing one to carry no load?

why have a big bathroom and put the toilet in a clost-sized room?

why use an exhaust fan to remove moisture from the whole bathroom instead of enclosing the bath/shower and removing it at it’s source?

why use (labor-intensive)concrete forms for a foundation when icf’s could be used to alleviate covering the same area 3 times, 1- to form, 2- to strip, 3- to insulate?

why use drywall with the 2-3 finish coats if you could spray shotcrete on in 1?

why put a washer and dryer in the basement when you dress/undress in the bedroom or bathroom that isn’t in the basement?

I’ve had numerous discussions about these things with people ranging from architects to carpenters, and noone has has to this date given me any adequate answers. Processes and materials are ALWAYS more predictable and reasonable than people. I always teach anyone that works for me to work smart not hard, use the right tool for the right job, and to tell me what you can’t do as opposed to what you can…I’ll figure that out soon enough. The people that are going to read this are probably the only ones to relate or know what I mean, or are curious or have the initaitve to want to make the changes that the building industry needs. The mentality of doing something even if it’s wrong, or just because that’s the way we’ve always done it, doesn’t fly anymore. Change is always resisted, but it’s also inevitible.

By: chad

chad — Mon, 05 Jan 2009 19:53:07 +0000

Goran – Great comments. I couldn’t agree more with your stressing the importance of the envelope. That’s the key to an energy efficient home, period IMHO.

Check out our post a while back on an Alternate Solar Thermal System for more insight into what you are touching on in your comments.

By: chad

chad — Mon, 05 Jan 2009 19:49:47 +0000

Tom – Great comment. Thanks for the insight into the envelope design. We are focusing on the Passive House concept of super-insulation for our next project, but the double envelope is still bouncing around in my head. I think a cool multi-family could be built with the concept.

By: tom toolbag

tom toolbag — Sun, 04 Jan 2009 16:11:25 +0000

WOW! I have been browsing this site for about 4-5 hours now, and found some things that I can relate too. There are a lot of ideas and info here, what a breath of fresh air!
I found another posting refering to a design with 2 envelopes, or 2 walls, by zero energy design. I built a house like this in 1985 for my parents and that design works very well. Goran brought up the idea of using water as a heat sink, we used river-rock. The house had a basement, and there was a pit roughly 20′x 10′ full of river-rock with ceramic tile above it. The south side had casement windows with a “sunroom”, and the heat would transfer into the rock, and when the temperature changed/inverted it would rise up into the air space(the space between the exterior and interior walls). I thought that water could be used also, but how to cover or transfer heat to it directly. This worked really well, and other than the three concrete walls of the pit, it was fairly cheap. They wanted a basement anyway, and in that region(just outside Moline, Il.)you gain ambient temps from one also. The house had NO furnace or a/c, 50g elect. w/h, electric baseboard heat with a stat in each room. This house cost $45.00 p/m to heat, and never got above 68-69 degrees in the summer. They had planned on putting thermal blankets(curtains) on the windows but never got around to it. The biggest problem was fresh air and humidity. My step-dad was too cheap to pay for a hrv/erv, but they were pretty expensive also then. Ironically, he later had a job as a hvac salesman and could have got one at cost and he wouldn’t part with the money. This house was built(with 2 1/2 acres) for $50,000.00 in 85, so that’s an idea how costly it was. When they sold after 13 years, it sold in 4 days for about $262,000.00. I wanted to buy it but couln’t match that offer……besides the fact that Icould build it for a lot less!
I have designed a house with same wall system(it’s called an envelope house) but a MAJOR obstacle is sizing the hvac system. It will be built off-grid, so relying on electric is not an option. Finding systems small enough or properly sized baffles building departments and they throw a wrench in the system. A hrv/erv system would ALMOST totally supply the needs, but they won’t let that fly. Back-up after back-up systems is all they know.
Anyway, I would rather spend more money on the walls or envelopes than mechanicals. Walls don’t wear out, or need repairs.